IQ optical modulator

Abstract

An IQ optical modulator including: a parent Mach-Zehnder type (MZM) optical waveguide; child MZM optical waveguides constituting two arms of the parent MZM; two electrode transmission lines provided along the two arms of the child MZM, respectively, and receiving modulation signal to phase-modulate an optical signal; an RF extension line connected to the two electrode transmission lines, respectively; a first optical splitter branching light into the two arms of the parent MZM; a second optical splitter branching light into the two arms of the child MZM; and a first optical multiplexer multiplexing light from the two arms of the child MZM, wherein stripe direction of the child MZM optical waveguide is same as the RF extension line, the second optical splitter, and the first optical multiplexer, and is orthogonal to the first optical splitter.

The invention claimed is: 
     
       1. An IQ optical modulator, comprising:
 a parent Mach-Zehnder type (MZM) optical waveguide functioning as a parent; 
 child MZM optical waveguides functioning as a child that constitute two arms of the parent MZM optical waveguide; 
 two electrode transmission lines that are provided along two arms of the child MZM optical waveguides, respectively, and that receive a modulation signal to thereby phase-modulate an optical signal propagating in the child MZM optical waveguides; 
 an RF extension line that is connected to the two electrode transmission lines, respectively, and that is used to input the modulation signal applied to the two electrode transmission lines; 
 a first optical splitter for branching light into the two arms of the parent MZM optical waveguide; 
 second optical splitters for branching light into the two arms of the child MZM optical waveguides; 
 first optical multiplexers for multiplexing light from the two arms of the child MZM optical waveguides, 
 wherein:
 the child MZM optical waveguides including the two electrode transmission lines has a stripe direction that is:
 the same as a stripe direction of the RF extension line, a stripe direction of the second optical splitter, and a stripe direction of the first optical multiplexer, and 
 orthogonal to a stripe direction of the first optical splitter; and 
 
 
 a second optical multiplexer for multiplexing light from the two arms of the parent MZM optional waveguide, and 
 wherein the stripe direction of the child MZM optical waveguides including the two electrode transmission lines is orthogonal to a stripe direction of the second optical multiplexer. 
 
     
     
       2. The IQ optical modulator according to  claim 1 , wherein:
 the two electrode transmission lines and the RF extension line connected to the two electrode transmission lines are configured by a differential coupling transmission line, and 
 a modulation signal applied from the RF extension line to the two electrode transmission lines is a differential signal. 
 
     
     
       3. The IQ optical modulator according to  claim 1 , wherein two parent MZM optical waveguides, which include the parent MZM optical waveguide, are integrated in a parallel manner within the same semiconductor element, the IQ optical modulator further comprising:
 an XY polarized wave separation optical splitter for separating an optical signal for the input to the two parent MZM optical waveguides to an X polarized wave and a Y polarized wave to input the separated waves. 
 
     
     
       4. The IQ optical modulator according to  claim 1 , wherein:
 a differential input/output-type high-frequency amplifier is provided in the same package as that of the IQ optical modulator, and the IQ optical modulator and the high-frequency amplifier are directly electrically connected only via a gold wire.